From time to time, the surfaces of roads, highways, bridges, parking lots, dock walls and the like must be replaced. Constant exposure to traffic and weather limits the useful life of such surfaces and resurfacing is necessary. In many instances, a new surface cannot simply be applied to the old surface. In some instances, there may be a structure above the surface. In order to maintain a minimum predetermined clearance between such structure and such surface (for the passage of trucks and other vehicles, for example), the surface cannot be built up. Rather replacement is necessary. In other instances, the addition of a new surface on top of the old may increase the dead weight of the structure above its design capacity. In such an instance, replacement of the surface is necessary. As well, in most instances, a satisfactory bond between a sound old surface and the new surface is required.
In yet other cases, it may be desirable to build or join a new concrete structure to an old concrete structure. In order to ensure a strong connection therebetween, the old surface of the original structure may have to be removed.
Various methods and devices exist for removing a concrete surface from a concrete structure.
A common such device is a pneumatic jack hammer. Jack hammers suffer from numerous disadvantages when used to remove a large surface area. They make a substantial amount of noise and vibration, which may greatly inconvenience the public. A single jack hammer can only be effectively used to break up a relatively small surface. Consequently, a large number of hammers and human operators are needed to remove a large surface area within a reasonable amount of time. These labour and equipment requirements add significantly to the cost of the surface removal. An operator, being in close proximity to the hammer and to its dust and debris, may be exposed to health and safety hazards. Furthermore, jack hammers may damage, not only the substrate beneath the concrete surface, but also any reinforcing bars or mesh embedded in the concrete. Vibrations may damage neighbouring concrete structures that are sound and not intended for removal, for example, by causing micro-cracks which can then propagate through sound concrete to cause premature deterioration to be initiated.
Rotary cutters suffer from similar problems and in addition are subject to significant wear and are slow.
In order to overcome the above problems, devices using pressurized water have been proposed. In this specification, a pressure of less than 10,000 psi will be described as high pressure. A pressure between 10,000 and 25,000 psi will be described as extra or very high-pressure. A pressure above 25,000 psi will be described as ultra-high pressure.
In one such known pressurized water device, a stream of ultra-high pressure water essentially cuts or erodes away the concrete. Such devices are to be contrasted with those devices which use much lower pressures and which are only able to be used to clean and scour a surface. In a known concrete-removing device as, for example, disclosed in U.S. Pat. No. 4,081,200, water is pressurized to between 25,000 and 60,000 psi, that is to the ultra-high pressure range. In contrast, in the known concrete scouring devices, high pressures or even pressures up to about 15,000 psi have been used. Conventional devices have not generally been able to make use of extra-high pressures for the satisfactory removal of concrete.
In the known concrete-removing device, the ultra-high pressure water is passed through at least one small diameter nozzle to form a high energy water jet. Water jets developed from such ultra-high pressures may be sufficient to remove all structural concrete, both sound and unsound, to depths up to at least 3 inches.
In the system of U.S. Pat. No. 4,081,200, the jet nozzle was directed at a predetermined fixed angle, and traversed along an arcuate path. The jet was extremely fine and produced essentially a cutting action, removing a narrow, but deep portion of concrete. Broken concrete apparently created a problem, and the system was designed to progressively remove it. In order to use these ultra-high pressures, the nozzle was extremely fine, and located close to the work face.
The ultra-high pressures involved resulted in high kinetic forces sufficient to break up sound concrete. This, however, is not always necessary, or even desirable. Such a known device removed old concrete--both sound and unsound--leaving a generally level surface upon which new concrete could be poured. An important disadvantage of such known device is that significant time and energy may be wasted on the removal of sound concrete, when it may not be necessary to do so. Extra cost will then be incurred in replacing, unnecessarily, the sound concrete.
Another disadvantage is that the vehicle, upon which the ultra-high pressure device is mounted, must be advanced at a generally constant, yet slow, rate of speed, in most instances, a human operator would be unable to effectively control the vehicle speed for efficient concrete removal. Therefore, an expensive automatic speed controlling mechanism must be used.
Yet another disadvantage is that the nozzle assembly, which is only a fraction of the width of the vehicle, must be positioned at a particular location on its frame. During operation, the assembly is fixed relative to the vehicle. The nozzle assembly can generally only remove concrete from an area directly beneath itself. Consequently, concrete can only be removed across a fraction of the width of the vehicle.
In order to overcome the above disadvantages, it would be advantageous to provide a pressurized-water concrete-removing device suitable for removing essentially only unsound concrete from the surface of a concrete structure. Such operation would be analogous to the removal of a decayed area in a tooth by a dentist. Essentially, only the decayed or unsound portion would be removed, leaving only the sound material. A relatively small amount of sound material might incidentally be removed to ensure that all of the unsound material had been removed. Such operation would allow for increased speed of concrete removal and lower cost and yet provide a suitable substrate surface, upon which a new surface could be placed.
The ultra-high pressure concrete-removing device described above could conceivably be operated by hand to remove only unsound material, much like the manner in which a dentist manipulates his drill by hand. However, because of the difficulty and slow speed of manually identifying and removing all areas of unsound concrete, such operation would not be practical. Automatic operation is preferable, but automatic operation of the ultra-high pressure device removes all concrete down to a particular level.
It would, therefore, be advantageous to provide an automatic device which would treat both the sound and the unsound concrete in the same way at the same time.
Preferably such a device would traverse over good and bad concrete alike, and would remove all of the bad, but only minor portions of the good concrete.
In this way, when a new surface was applied, the quantity of new material required for resurfacing would be minimized. Also, the volume of loose, dislodged old material, which would have to be removed, would be minimized.
Preferably, the system would provide a degree of sweeping action or disruption which would carry dislodged material away from the work face. Kinetic forces would be sufficient to break up unsound concrete, while high volume flow rates in a disruptive flow pattern would effectively carry loose debris away from the immediate vicinity of the work face.
It would also be advantageous to provide a device which could also be operated manually, if so desired. While automatic operation is advantageous, it may be desired to use the device to remove only small, unconnected patches of unsound concrete. In such cases, manual operation of the device may be preferred.
It would also be advantageous to provide a concrete-removing device that allows a vehicle, upon which the device is mounted, to remain stationary or that requires it to be move only intermittently.
A further advantage would be obtained by providing for a nozzle assembly that traversed across at least a significant portion of the width of the vehicle.
A concrete-removing device using pressurized water and possessing the above advantages, of course, would also have all the advantages of a pressurized water system over standard pneumatic jack hammer or rotary concrete-removal devices.
It would further be advantageous to provide an apparatus or device which would be effective to break up unsound concrete beneath reinforcing bars embedded in such concrete so as to allow new replacement concrete to be introduced into the space below such reinforcing bars to ensure in turn the provision of adequate strength in the repaired structure. In this respect, it would also be advantageous if such an apparatus were also effective to clean all surfaces, including the undersurfaces, of such reinforcing bars, so as to ensure proper bonding of the new concrete material to those bars and to reduce, if not eliminate, the future deterioration of the replacement concrete as can be initiated by the presence of uncleaned and corroded reinforcing bars.
Yet another desirable feature of such an apparatus would be for it to be adaptable for the removal of unsound concrete material from sloping rampways such as are found, for example, between the different levels of indoor parking buildings.
A further desirable feature of such an apparatus would be for it to be usable for removing unsound concrete material from other non-horizontal surfaces. There may, for example, be mentioned the use of such an apparatus for removing unsound concrete material from the interior and exterior walls of buildings as well as in the treatment of dock walls and the walls of locks as provided in canal systems.
For speedier operation and further to avoid the risk of removing sound concrete material, it would be desirable to have an apparatus which could be programmed to treat an area of concrete work surface having an irregular outline in circumstances where it was established that only the concrete within such an irregular outline needed to be removed.